This invention pertains to the art of solvent blends and solvent/resin blends. More particularly, this invention pertains to blends that reduce the atmospheric reactivity of some high volatile organic compounds. The invention is particularly applicable to solvent blends and solvent/resin blends that combine volatile organic compounds with newly discovered zero volatile organic compounds for use adhesives, coatings, inks, cleaning and blowing agents and the like and will be described with particular reference thereto. However, it will be appreciated that the invention may be advantageously employed in other environments and applications.
Heretofore, hydrocarbon-based solvents have been used to dissolve organic materials in many industrial applications. However, recently, hydrocarbon-based solvents have fallen out of favor because they have been classified by the United States Environmental Protection Agency and other international regulatory bodies as materials that contribute to the formation of ground based ozone or smog. This has created a need for other types of solvents for the production of coatings, adhesives, inks and the like.
Upon evaporation, a highly-reactive, hydrocarbon-based solvent reacts with hydroxyl radicals and ultraviolet light very close to the ground to form a photochemical smog that is considered harmful and in some cases dangerous. Some cities have severe smog which reduces visibility and actually causes "ozone alerts." In part, the smog is caused by hydrocarbon emissions from cars. However, another major contributor is industrial use of hydrocarbon-based solvents such as hexane and toluene.
For the purpose of ozone excedence in cities throughout the United States, a reactivity based formulation scheme will also be described which will make use of low atmospheric reactivity solvents by themselves or in combination with high reactivity solvents. These solvents and solvent blends can be used to dissolve resins for adhesives, inks and coatings, or used as cleaning agents and in the process reduce the amount of ozone formed in the lower atmosphere.
The benchmark for desired reaction rates of hydrocarbon-based compounds is ethane. If a compound has a reaction rate with the hydroxyl radical and ultraviolet ("UV") light that is faster than ethane, the compound reacts too close to the ground and consequently generates ozone and smog. Such compounds are defined as volatile organic compounds (VOCs). On the other hand, if a compound has a reaction rate that is slower than ethane, the compound reaches higher into the atmosphere before reacting with the hydroxyl radical and UV light. In such instances the non-VOC compound does not contribute to the formation of ground based ozone and smog.
Governmental regulations limit the use of VOCs in coatings, inks, and adhesives. As a result, water-borne coatings have become the most important type of coatings in coating and adhesive systems. However, water-borne coatings must contain some volatile organic compound content. This is because water flashes off too fast from the water-based latex or emulsion to make a good film. To alleviate this problem, 7% to 10% of a slower evaporating solvent such as a glycol ether is added to the latex to aid in film formation. Unfortunately, glycol ethers are primary examples of VOCs and thus dangerous to the environment.
Halogenated hydrocarbon-based compounds have reaction rates that are slower than ethane. However, these halogenated compounds are ozone depleting consequently, they are not suitable VOC-free solvents.
In the prior art, U.S. Pat. No. 5,102,563 to Desbiendras describes a solvent composition which contains methyl tert butyl ether. However, methyl tert butyl ether is a VOC and thus unsafe for the environment. Similarly, U.S. Pat. No. 4,898,893 to Ashida describes a composition for making a blowing agent which contains a flammable aliphatic hydrocarbon. This is also a VOC. U.S. Pat. No. 3,950,185 to Toyama teaches film removing compositions which contain methylene chloride and bromochloromethane which are not VOCs. However, these compositions also contain methanol and monochlorobenzene which are VOCs. U.S. Pat. No. 3,924, 455 to Begishagen describes a formulation containing mineral spirits which removes lacquer stress coatings. These mineral spirits are also VOCs.
Use of a combination of a zero volatile compound with a highly reactive compound or with a low reactivity compound will reduce the overall VOC content of the mixture when used for the applications mentioned. Also, various low reactivity VOC solvents have been identified which when used with resins, will reduce the atmospheric reactivity of the coating, ink or adhesive. The low reactivity solvents can be blended with high reactivity solvents before mixing with a resin to lower the total reactivity of the formulation. Thus, the highly reactive compounds become less reactive than just a subtractive effect in some instances. In other examples, it takes a larger amount of the zero volatile organic compound to give the desired effect of reducing the incremental reactivity of the mixture closer to 0.25, which is the value measured for ethane.
Some highly reactive VOC solvents do not realize the same degree of VOC activity reduction according to the present application as other VOCs. Examples of these are formaldehyde, methyl nitrite, trans-2-butene, and 1,3,5-trimethylbenzene. These compounds are so reactive that addition of a zero VOC compound will have little or no effect on the reactivity of the mixture. A first object of the present invention is to provide a reduction in atmospheric activity of high VOC solvents by adding a zero VOC solvent to the high VOC solvent. An additional aspect to the present invention involves producing environmentally friendly coatings, inks, adhesives, blowing agents and cleaning agents by adding a zero VOC solvent to a high VOC solvent containing coating, ink, adhesive, blowing agent or cleaning agent.
A first object of the invention is to provide a reduction in atmospheric reactivity of high VOC solvents by addition of a low reactivity or zero VOC solvent to the high VOC solvent.
An additional aspect of the present invention involves producing environmentally friendly coatings, inks, adhesives, blowing agents and cleaning agents by adding a zero VOC or low reactivity solvent to a high VOC solvent containing coating, ink, adhesive, blowing agent or cleaning agent.
A further object of the present invention is the identification of some high-performance solvents and solvent/resin blends which are non-flammable or self-extinguishing and do not contribute to the formation of ground-based ozone.
Another object of the present invention are solvents and solvent/resin blends that are safer to the environment than even waterbased systems which still must contain a volatile organic solvent to aid in film formation.
Yet another object of the present invention are environmentally-safer solvent compositions which do not contribute to the formation of ground based ozone which will be useful in the formulation of cleaning agents, coatings, adhesives, inks and also blowing agents for the production of plastic foams.